Copolymers of alpha-methylstyrene and styrene and uses thereof

ABSTRACT

This specification discloses manufacture of copolymers of alpha-methylstyrene and styrene in which the alpha-methylstyrene may range from about 50 to 90% and the softening point may range from about 60° to 100° C. The copolymers have especial utility with elastomers to produce pressure sensitive adhesives and the like, and in hot melt coatings.

This is a division of application Ser. No. 333,215, filed Feb. 16, 1973,now U.S. Pat. No. 3,932,332.

This invention relates to the manufacture of copolymers ofalpha-methylstyrene and styrene and uses thereof. More particularly itrelates to the use of such polymers as tackifiers for synthetic rubbers,as constituents of hot melt coatings and adhesives, and other uses.

The preparation and use of a variety of resins based upon a styrenemonomer is well known. We have discovered that copolymers ofalpha-methylstyrene and styrene prepared under controlled conditionsexhibit special and unexpected usefulness in a number of differentareas. Such polymers impart good tack to styrene-butadiene rubbersthereby producing good pressure sensitive adhesives, mastics, caulks,and sealants. The polymers of the invention may also be used to imparttack to elastomeric block copolymers of styrene and isoprene and topolychloroprene elastomers to produce adhesives. Some, but not all ofthe polymers, are also effective as constituents for hot melt coatingsand adhesives where they exhibit good compatibility and low cloud pointwhen blended into the mix. The polymers are also useful as additives topaint and chemical coatings.

We prepare a copolymer of alpha-methylstyrene and styrene ranging fromabout 50% alpha-methylstyrene and 50% styrene to about 90%alpha-methylstyrene and 10% styrene. We blend the monomers in a solventand react them in the presence of a Friedel-Crafts catalyst. Wecarefully control the temperature of the reaction mixture and maintainthe temperature within close limits throughout the time of reaction. Wereact the mixture at a selected temperature within a range of about 15°to 45° C. Lime is then added to the reaction mixture to neutralize thecatalyst. After filtration of the catalyst residue, the solvent isstripped from the resin. The resin so produced has a softening point(ring and ball) ranging from about 70° to 100° C. Preferably we preparea polymer of about 70% to 75% alpha-methylstyrene and 30% to 25%styrene. We prefer to react the monomers at a selected temperaturewithin a range from about 15° to about 33° C., and we prefer to maintainthe reaction temperature within limits of ± 2° C. Under somecircumstances we may react the monomers at a selected temperature withina range of 23° to 33° C. and we may maintain the reaction temperaturewithin limits of ± 1° C. We prefer to use boron trifluoride (BF₃) as acatalyst.

The resin is useful as an additive for styrene-butadiene rubber (SBR),block copolymers of styrene and isoprene, and polychloroprene. The resinimparts tack to those elastomers. The compositions of resin andelastomer are suitable for use as pressure sensitive adhesives, mastics,sealants, and caulks.

Hot melt compounds are commonly used for sealing and as adhesives. Suchcompounds are frequently used to seal corrugated shipping containers andthe like and they are especially useful because they are thermoplastic.They may be applied hot to corrugated paper but will almost immediatelyset because of quick loss of heat. The compounds do not include solventswhich could cause fumes or degradation of the corrugated paper. Weprefer to employ in hot melt compounds one of our resins having asoftening point (ring and ball) from about 70° to about 85° C. Suchresins exhibit exceptional compatibility with paraffin wax and ethylenevinyl acetate commonly used in hot melt compositions and exhibitdesirably low cloud points. In certain hot melt formulations the resinof the invention having a softening point of about 100° C. has utility.

The invention may be illustrated by reference to several exemplaryresins manufactured and used in accordance with the invention.

EXAMPLE 1

A 500 milliliter three neck flask is equipped with a stirrer,thermometer, gas outlet tube, and a straight pipe dip tube. The flask ischarged with 70 grams of alpha-methylstyrene 30 grams of styrene and 100grams of Solvesso 100. The mixture is cooled to 15° C. BF₃ gas isintroduced into the mixture at a flow rate of approximately 0.1 gram perminute from time to time over a period of 12 minutes while maintaining atemperature in the reaction mixture of 15° to 20° C. through use of adry ice alcohol bath at -15° C. After reaction, the mixture turns to apale yellow color and is allowed to soak at 15° to 20° C. for 30minutes. Thereafter the mixture is quenched with approximately 5 gramsof lime. Twenty grams of Filter Aid is added and the mixture heated toapproximately 55° C. The mixture is then vacuum filtered through FilterAid. One hundred milliliters of xylol is used to rinse the flask andthen to wash the filter cake. The resin oil is transferred to a singleneck round bottom flask fitted with a cork containing a gas dip tubethermometer and an exhaust tube. The mixture is stripped of solvent at apot temperature of 210° C. under nitrogen and is then steam stripped toa maximum pot temperature of 225° C.

The resin thus produced has the following properties:

    ______________________________________                                        Softening Point (R&B) 98° C                                            OMS* Cloud Point      95° C                                            Nujol Cloud Point     20° C                                            60% Solution Viscosity                                                        (In Toluene)          0.9 Stokes                                              70% Solution Viscosity                                                        (In Toluene)          6.6 stokes                                              ______________________________________                                         *odorless mineral spirtis                                                

EXAMPLE 2

Seventy-five grams of alpha-methylstyrene and 25 grams of styrene arecharged to a flask with 200 grams of Solvesso 100. The procedure issimilar to that of Example 1. BF₃ is added from time to time over a 10minute period while maintaining a temperature in the reaction mixture of25° ± 2° C. After saturation of the mixture by BF₃ is noted, the mixtureis allowed to soak for 30 minutes at 25° ± 2° C. The resin thus producedhas the following properties:

    ______________________________________                                        Softening Point (R&B) 87° C                                            Color                 Water White                                             OMS Cloud Point       33° C                                            Nujol Cloud Point     4° C                                             70% Solution Viscosity                                                        (In Toluene)          2.6 Stokes                                              ______________________________________                                    

EXAMPLE 3

A mixture of 375 grams of alpha-methylstyrene, 125 grams of styrene and1,000 grams of Solvesso 100 is charged to a flask. The proceduregenerally follows that of Examples 1 and 2 except that the time forsaturation with BF₃ is 21 minutes. The reaction temperature ismaintained at 31° ± 1° C. and the mixture is allowed to soak for 1 hourat 31° ± 1° C. following saturation.

The properties of the resin so produced are as follows:

    ______________________________________                                        Softening Point (R&B) 70° C                                            Color                 Water White                                             OMS Cloud Point       5° C                                             Nujol Cloud Point     Clear at 0° C                                    70% Solution Viscosity                                                        (In Toluene)          1.7 Stokes                                              ______________________________________                                    

It is apparent that the polymerization temperature is related to thesoftening point of the resin, the softening point decreasing as thepolymerization temperature is raised. It is believed that close andaccurate control of the polymerization temperature produces a polymerhaving a generally uniform molecular weight. It is thought that theeffectiveness of the resin may be due, at least in part, to itsparticular molecular weight distribution.

The usefulness of the resins may be shown by reference to test data. Ithas been found that the resins of the invention impart good tack to SBR,Neoprene AC, and Kraton 1107. Several resins prepared in accordance withthe general procedures set forth in Examples 1, 2, and 3 were separatelyblended with SBR in varying proportions. The mixtures of resin andrubber were then applied to film, and tack data on tapes cut from thisfilm were obtained following standard test procedures as shown in Tables1, 2, and 3.

                  TABLE 1                                                         ______________________________________                                        Tack Data - Pressure Sensitive Tapes - Different Resins                       And SBR in Varying Proportions                                                                Resin  Resin    Resin                                                         Typical                                                                              Typical  Typical                                                       of Ex. 1                                                                             of Ex. 2 of Ex. 3                                      ______________________________________                                        30% Resin/                                                                    70% SBR                                                                       Polyken       Gms.             700    600                                     180° Peel                                                                            Ozs.             46     52                                      90° Quick Stick                                                                      Ozs.              5     920                                     178° Hold to Steel                                                                   Mins.            1250   920                                     40% Resin/                                                                    60% SBR                                                                       Polyken       Gms.    980      875    890                                     180° Peel                                                                            Ozs.    50       48     56                                      90° Quick Stick                                                                      Ozs.     8        6     17                                      178° Hold to Steel                                                                   Mins.   >1440    570    455                                     50% Resin/                                                                    50% SBR                                                                       Polyken       Gms.             1320   1150                                    180° Peel                                                                            Ozs.             56     61                                      90° Quick Stick                                                                      Ozs.             16     28                                      178° Hold to Steel                                                                   Mins.            425    260                                     ______________________________________                                    

                  TABLE 2                                                         ______________________________________                                        Tack Data - Pressure Sensitive Tapes -                                        50% Resin Typical of Example 2                                                and 50% Neoprene AC - soft                                                    Polyken           gms.       2130                                             180° Peel  ozs.       100                                              90° Quick Stick                                                                          ozs.       Harsh                                            178° Hold to Steel                                                                       mins.      >8000                                            ______________________________________                                    

                  TABLE 3                                                         ______________________________________                                        Tack Data - Pressure Sensitive Tapes -                                        Resins Typical of Examples 2 and 3                                            And Kraton 1107                                                                                  Resin 2 Resin 3                                            ______________________________________                                        30% resin/70% polymer                                                         Polyken         gms.   1220       980                                         180° Peel                                                                              ozs.   50         40                                          90° Quick Stick                                                                        ozs.   38         28                                          178° Hold to Steel                                                                     mins.  >3000      >3000                                       40% resin/60% polymer                                                         Polyken         gms.   1520       1220                                        180° Peel                                                                              ozs.   74         58                                          90° Quick Stick                                                                        ozs.   36         48                                          178° Hold to Steel                                                                     mins.  >3000      >3000                                       50% resin/50% polymer                                                         Polyken         gms.   No Tack    1500                                        180° Peel                                                                              ozs.   "          80                                          90° Quick Stick                                                                        ozs.   "          56                                          178° Hold to Steel                                                                     mins.  "          >3000                                       60% resin/40% polymer                                                         Polyken         gms.   No Tack    280                                         180° Peel                                                                              ozs.   "          90                                          90° Quick Stick                                                                        ozs.   "          0                                           178° Hold to Steel                                                                     mins.  "          >3000                                       70% resin/30% polymer                                                         Polyken         gms.   No Tack    No Tack                                     180° Peel                                                                              ozs.   "          "                                           90° Quick Stick                                                                        ozs.   "          "                                           178° Hold to Steel                                                                     mins.  "          "                                           ______________________________________                                    

Certain of the resins are effective in hot melt coatings and adhesives.Clouding of the hot melt composition indicates a phase separation and,consequently, a loss of solubility. Accordingly, it is desirable in suchcompositions that the cloud point be low. The freezing point of paraffinwax, a major constituent of many hot melt coatings, is about 154° to158° F. and the cloud point of such hot melt compositions is usuallypreferably near that temperature. However, there are applications, suchas in high hot strength coatings or adhesives, in which completesolubility is not desirable.

A common hot melt composition comprises ethylene vinyl acetate and wax.Several resins exemplary of Examples 2 and 3, identified as resins 2 and3 respectively, were blended with wax and ethylene vinyl acetate. Theproperties were maintained constant, but the amount of vinyl acetate inthe ethylene vinyl acetate was varied and cloud point determinationswere made as shown in Table 4. The data show that there is a wide rangeof vinyl acetate content in which the cloud point is close to thefreezing point of the wax.

                  Table 4                                                         ______________________________________                                        Cloud Point Determinatins In Degrees F.                                       For Blends Of 20% Ethylene Vinyl Acetates,                                    20% Resin, and 60% Wax With Varying                                           Ratios Of Ethylene And Vinyl Acetate                                          In The Copolymer                                                              % Vinyl acetate (in ethylene vinyl acetate)                                   18           25       28       33     40                                      ______________________________________                                        Resin 2 194      169      158    169    255                                   Resin 3 158      158      154    162    248                                   ______________________________________                                    

Exemplary resins were blended with several waxes in differentproportions, and the cloud points were determined with the results shownin Table 5.

                  Table 5                                                         ______________________________________                                        Cloud Point Determinations in Degrees F. For                                  Blends of Wax and Resin in Varying Proportions                                       % Wax                                                                         30(1)   50(1)     70(1)     50(2)                                      ______________________________________                                        Resin 2  158       172       194     226                                      Resin 3  154       153       156     180                                      ______________________________________                                         (1)Atlantic 1116, manufactured by Atlantic Refining Co.                       (2)Multiwax 180-M, manufactured by Sonneborn Div. of Witco Chemical Corp.

Exemplary resins were blended with wax and with ethylene vinyl acetate(72% ethylene and 28% vinyl acetate) in varying proportions and cloudpoint determinations were made as shown in Table 6. Again, low cloudpoint was found over a broad range of proportions.

                  Table 6                                                         ______________________________________                                        Cloud Point Determinations In Degrees F                                       For Blends of Wax, Resin, and Ethylene                                        Vinyl Acetate (72% Ethylene and 28%                                           Vinyl Acetate) in Varying Proportions                                         EVA          15%        20%        25%                                        Resin       15         20         25                                          Wax         70         60         50                                          ______________________________________                                        Resin 2     172        158        158                                         Resin 3     158        154        158                                         ______________________________________                                    

Exemplary resins were blended with ethylene vinyl acetate (72% ethyleneand 28% vinyl acetate) and wax with the amounts of wax and resin beingvaried. Cloud point determinations were made as shown in Table 7.

                  Table 7                                                         ______________________________________                                        Cloud Point Determinations In Degrees F.                                      For Blends of Wax, Resin, and Ethylene                                        Vinyl Acetate (78% Ethylene and 28%                                           Vinyl Acetate) in Varying Proportions                                         EVA      20%      20%      20%    20%    20%                                  Resin   10       20       30     40     50                                    Wax     70       60       50     40     30                                    ______________________________________                                        Resin 2 158      158      169    169    172                                   Resin 3 158      154      154    156    158                                   ______________________________________                                    

Several hot melt compositions were prepared including resins exemplaryof Examples 1, 2 and 3. Those compositions were then tested forviscosity, effectiveness in adhering two sheets of corrugated cardboard,and softening temperature. The data are set forth in Table 8.

                  Table 8                                                         ______________________________________                                        Blend                                                                         Resin 1    --       --      --     --    37.5%                                Resin 3   37.5%    37.5%    --     --     --                                  Multiwax  24.4     24.4    24.4   24.4   24.4                                 180-M(1)                                                                      Resin 2    --       --     37.5   37.5    --                                  Elvax 460(2)                                                                            24.8     24.8    24.8   24.8   24.8                                 Polyethylene                                                                  AC-8(3)    --       --     13.1    --    13.1                                 Polywax    --      13.1     --    13.1    --                                  1000(4)                                                                       BHT(5)    0.25     0.25    0.25   0.25   0.2                                  Viscosity                                                                     cps a 250° F                                                                     18,000   12,000  29,750 14,600  --                                  cps a 275° F                                                                     10,900    7,300  12,500  8,300  --                                  cps a 300° F                                                                      7,000    4,675   7,500  5,300 13,700                               cps a 325° F                                                                      4,700    3,200   5,000  3,550  --                                  cps a 350° F                                                                      3,250    2,250   3,450  2,450 5,070                                Corrugated                                                                    Test                                                                          a -20° F                                                                         F.T. (6) F.T.    F.T.   F.T.   F.T.                                 a Ambient F.T.     F.T.    F.T.   F.T.   F.T.                                 Temp.                                                                         a 140°  F                                                                        F.T.     F.T.    F.T.   F.T.   F.T.                                 a 150° F                                                                         F.T.     F.T.    F.T.   F.T.   F.T.                                 a 160° F                                                                         F.T.     F.T.    F.T.   F.T.   F.T.                                 a 165° F                                                                         Cohesive F.T.    Border-                                                                              Border-                                                                               --                                            Failure          line   line                                        B & R Softening                                                                         113° C                                                                          111° C                                                                         111° C                                                                        110° C                                                                         --                                  Point                                                                         ______________________________________                                         (1)Microcrystalline wax, Sonneborn Div. of Witco Chemical Co.                 (2)Ethylene vinyl acetate (18% vinyl acetate) E.I. DuPont deNemours           (3)Allied Chemical Corp.                                                      (4)Synthetic Paraffin Wix, Bareco Corp.                                       (5)Butylated Hydroxytoluene                                                   (6)Fiber Tear                                                            

We have disclosed certain preferred embodiments of our preferred resinsand uses thereof. It is to be understood, however, that we do not limitourselves thereto and that the invention may be otherwise variouslypracticed within the scope of the following claims.

We claim:
 1. A new composition of matter comprising a blend of (A) anelastomer selected from the group consisting of styrene-butadienerubber, block copolymers of styrene and isoprene, and polychloropreneand (B) a copolymer of α-methyl-styrene and styrene having a softeningpoint (ring and ball) between 60° and 100° C., said component (B) beinga copolymer produced by the copolymerization of, by weight, from about90% to about 50% of α-methylstyrene and from about 10% to about 50% ofstyrene at a temperature range from about 15° C. to about 45° C. in thepresence of a Friedel-Crafts catalyst.
 2. The composition of claim 1wherein component (B) is a copolymer produced by copolymerizing fromabout 75% to about 70% of α-methylstyrene and from about 25% to about30% of styrene at a temperature range from about 15° to about 45° C. inthe presence of a Friedel-Crafts catalyst.
 3. The composition of claim 2wherein component (A) is styrene-butadiene rubber.
 4. The composition ofclaim 2 wherein component (A) is a block copolymer of styrene andisoprene.
 5. The composition of claim 2 wherein component (A) ispolychloroprene.